From "solar maximum" to "minimum" in one week

The number of sunspots changes with about 11 year cycles, and Sun is on the declining phase of its cycle 25. However, the solar activity may vary significantly even on a shorter time scales. Nine days ago (8 Aug. 2025, left) there were number of sunspots located mostly in the Northern hemisphere (upper part of the solar disk). This level of activity is typical for a solar maximum. However, today (17 August, 2025, right) there are only very few small pores situated mostly in the Southern hemisphere. Such low sunspot activity is more typical for the period of solar minimum. Why does it matter? The ultraviolet (UV) flux, which strongly correlates with sunspot activity, heats the Earth atmosphere. More sunspots mean the Earth’s atmosphere expands to higher altitudes, where it creates additional drug for low-Earth orbit (LEO) satellites. Such swings in number of sunspots may result in more LEO satellites being prematurely lost due to space weather.